[Pw_forum] further questions about 'nscf' and system control in 'nscf'

W. YU yuwen_66 at yahoo.com
Thu Dec 14 06:45:32 CET 2006

Thanks Stefano,

Now some other questions have come to my mind:

>'nscf' was in the past the only option for a non-scf
>calculation and 
>this  has been in the past a source of
>problems because it was used for 1) band structure
>calculation, 2)  BZ 
>refining in order to obtain nicer
>dos etc, and 3) preparation-run for phonon
>calculations and maybe other 
>uses as well...
>The needs of these different types of calculation
>are different... and 3) should be made, to be
>with exactly the same sampling
>as the  original scf calculation... 

Does this mean the k-point grid for 'phonon'
calculation should ALWAYS (at least in principle) be
the same as the 'scf' part? If so, what will happen if
it is not?

Now this also reminds me of questions about general
setup of SYSTEM control and K_POINTS for nscf
calculations including 'phonon','bands', and 'nscf'.

This is how I understant it: 
1. The ecut and ecutrho could be different from the
scf part concerning all the three nscf
calculations,even the smearing method and parameters
supplied when dealing with a metallic system.

2. The k-points can and really should be different for
band and dos type calculations. For phonon, I am not
sure,I need your confirmation.

3. If it is a spin-polarized calculation, if I already
set the starting_magnetization say equals 0.5, why
should I set it again in the band and other nscf
calculation since the selfconsistency is already
achieved and the magnetization is determined by the
scf cycle.

Best wishes,

Wen YU

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